(1) Field of the Invention
The present invention relates to a noise control of a high voltage electric wire, which is thick and allows a large current to flow therethrough.
(2) Description of the Related Art
A high voltage electric wire is used to supply electric power to a motor for traveling, which is mounted on an electric motor vehicle, a hybrid motor vehicle and so on (see Japanese Patent Application Laid-Open No. 2005-151712). The high voltage electric wire is a thick electric wire such as an electric wire having a central conductor of 20 mm square. The high voltage electric wire is electrically insulated from a low voltage electric wire. In the high voltage electric wire, a wire of a plus circuit and a wire of a minus circuit are arranged in parallel to each other.
A high voltage subjected to switching is applied on a high voltage electric wire. As for the high voltage electric wire, it is an important point that an excellent noise control effect can be obtained in a frequency range from a low frequency to a high frequency.
Since a large current flows through the high voltage electric wire, a magnetic field is generated in the vicinity of the high voltage electric wire. Depending on a case or a situation, such a magnetic field becomes a subject of restriction and requires to be controlled. As a method of controlling the magnetic field, to shield the magnetic field with a high magnetic permeability material is known. For example, a ferrite core, which has a high specific resistivity against a high frequency wave, is used. However, such a method has a problem that a product price becomes high and a problem, that is, a lack of flexibility and a lack of mounting workability.
As a technique to prevent an electromagnetic wave noise from radiating to the outside, to twist two wires (i.e. electric wires) together to form a twisted pair of the wires is generally known. That is, when a wire to form a plus circuit and a wire to form a minus circuit are twisted together, an action to remove the electromagnetic wave noise is increased. However, when the technique described above is to be applied, there is a problem that since the high voltage electric wire is thick, these two wires cannot be twisted together well so as to have the effect described above, that is, when being twisted together, it is impossible to obtain a small twist pitch.